This invention relates generally to xerographic-type copiers using photoconductive belts as the image medium and more particularly to a mounting arrangement for a segmented photoconductive belt for use in a xerographic or the like copier.
Electrostatic or xerographic-type copiers employing photoconductive segments mounted on endless belts and carried thereby past copy stations for imaging are known in the art. Such an arrangement is shown in U.S. Pat. No. 3,792,924, issued Feb. 19, 1974. That patent discloses an electrophotographic copying system which employs parallel spaced, endless belts between which light sensitive sheet segments are detachably attached at intervals thereabout. The belts are entrained about spaced rollers used to move the belts along an endless path. The sheet segments are transported by the moving belts past copier units provided for imaging the segments electrostatically, developing the electrostatic image and for transferring the image to a sheet of paper.
The segments are attached to the belts by means of rods which are passed through pockets formed at the ends of the segments. The ends of the rods are detachably received in channel-shaped supports affixed to the belts outside the path of travel of the segment.
While this arrangement for attaching photoconductive segments to endless drive belts in a copier may be satisfactory in some applications, there are certain disadvantages associated therewith. For one, due to the use of the channel-shaped supports which engage the rod ends, it becomes necessary to cam away the magnetic brush developer roll employed for developing the latent image on the segments as the ends of the segments pass thereby. This is to avoid application of developer material to the rod coupling means and thereby contaminating the machine components with such material. The latter disadvantage becomes even more critical in the case of a high speed copier wherein a multi-roll magnetic developer is employed. Also, because the support rods extending through the pockets of the photoconductive segments are attached only at the ends thereof, a non-uniform holding force across the ends of the segments is provided. This causes the segments to sag somewhat at the center thereof. This can be detrimental since optimum resolution requires the focal plane of the image and the photoconductive surface to be common.
Other printing plate mounting schemes for mounting metal or the like printing plates on the master cylinder of an offset or the like press are also known in the art, See U.S. Pat. Nos. 3,946,670; 3,941,055; and 3,970,001. These arrangements employ spaced bars extending axially of the cylinder along the surface thereof which include angled slots to receive the bent back edges of the metal plates for securing the plates on the cylinder surface. In the '670 patent, a spring loaded bar is provided at one end for tensioning of the plate while in the '001 patent a toggle arrangement is used for that purpose.
While these last-mentioned mounting schemes provide a uniform tension on the printing plate across the entire width thereof, they are employed to maintain the plate on a rigid substrate and not to suspend the plate between endless belts which carry the plate along a path between two drive rolls.
In a relatively wide photoconductor belt which is driven over rollers wherein there is a relatively short length to width ratio there exists a problem with "walking" or the tendency of the belt to move axially along the drums or rollers. This problem has been dealt with by a number of approaches, such as specially shaped rollers or by detecting the walking controlling and adjusting devices. These approaches are relatively complex, or introduce special problems for a photoresponsive copier belt.